Kamogawa Asumi always dreamed of becoming an astronaut. The space vehicle, transporting the Japan's youngest male astronaut to space, fell from the sky and crashed. Tragically, the accident also killed Asumi's mother. Mourning her death, Asumi meets the spirit of that astronaut, wearing the mask of a lion, calling himself Lion-san, who tells her stories of space. Listening to these stories, and with the full support of her hard-working father Tomorou, Asumi is encouraged to make her dream of becoming an astronaut a reality.